The present invention relates to an image forming apparatus and, more particularly, to an image forming apparatus capable of receiving and outputting a color image consisting of more than two colors.
An image forming apparatus, such as a digital copy machine, reads a color original image by using an optical-to-electrical converting element, such as a color CCD, and discriminates areas in accordance with color information of the original image, then forms an image corresponding to the discriminated areas whose colors are replaced by colors that are different from original colors (red and black, for example). Further, the suggested image forming apparatus separates a red component and black component, for instance, from the read color image signal, then expresses the original image by using two colors which differ from each other. In other words, the described image forming apparatus forms an image so that the red component is represented by a red color and the black component by a black color, for example.
However, in a case where copying is performed in two colors based on an input color image, if the conventional dot non-color mixing method (the method in which a plurality of colors are not printed at one dot) is employed, there is a problem in that the densities of color components which are not printed are not stored in a copied image, and that the density of the entire image is also not stored.
Although in order to solve the problem non-output data is diffused to the neighboring pixel data are to be outputted, in a case where the method includes a decision process such that the denser color out of the data of the two colors is chosen to be outputted, when an original image which is composed of an uniformly weak color and other strong color is copied, the weaker color is seldom outputted and the color data of the weaker color will not be outputted until the spreading value becomes a substantially large value. Accordingly, there is a problem in that the copied image looks rough.